Antiglare safety rearview mirror for automotive vehicles

ABSTRACT

In a day and night rearview mirror system for an automotive vehicle, whether an otherwise conventional inside or outside mirror or a periscope system, on a mirror over its horizontal extent and horizontally parallel to road as viewed in the image display, there is provided a middle band of reflectivity reduced to a degree that, for following headlights imaged to the driver in the band, the glare is diminished to a level which is not interfering to a safe driving night vision nor annoying to the driver; a sufficient width or vertical dimension of the band enabling the driver easily to bring imaged following headlights into, and with changing inter-vehicle spacing keep them within, the reduced reflectivity area by a slight head tilting.

United States Patent [191 Mills [54] ANTIGLARE SAFETY REARVIEW MIRRORFOR AUTOMOTIVE VEHICLES [76] Inventor: John Edward Mills, 15142 DrakeRoad, Strongsville, Ohio 44136 [22] Filed: Oct. 7, 1971 [21] Appl. No.:187,563

Eisenschink 350/278 X 11 3,738,737 June l2, l973 Primary Examiner-JohnK. Corbin Attorney-Philip D. Golrick [57] ABSTRACT In a day and nightrearview mirror system for an automotive vehicle, whether an otherwiseconventional inside or outside mirror or a periscope system, on a mirrorover its horizontal extent and horizontally parallel to road as viewedin the image display, there is provided a middle band of reflectivityreduced to a degree that, for following headlights imaged to the driverin the band, the glare is diminished to a level which is not interferingto a safe driving night vision nor annoying to the driver; a sufficientwidth or vertical dimension of the band enabling the driver easily tobring imaged following headlights into, and with changing inter-vehiclespacing keep them within, the reduced reflectivity area by a slight headtilting.

11 Claims, 5 Drawing Figures ANTIGLARE SAFETY REARVIEW MIRROR FORAUTOMOTIVE VEHICLES The attention given by the various standard-settingauthorities or bodies to indirect visibility systems including rearviewmirrors in automotive vehicles, and statistical studies indicating thatover one-fifth of all motor vehicle crashes to the extent of about some6 million crashes per year occur in the indirect field of view area tothe sides and rear, are themselves evidence of the importance of rearvision through rearview mirrors.

The problems presented to the driver, during nighttime driving of anautomotive vehicle, by headlight glare reflected in an inside or outside(so-called sideview") rearview mirror from a vehicle or vehicles to therear, are well known to any experienced driver. Where the rearviewmirror is set to the normal disposition or angle to which the driver isgenerally accustomed for optimum rearview or rear fleld imaging indaytime driving and with his normal posture, headlights of a followingvehicle, whether at a distance more or less fixed or varying as therearward vehicle is dropping back after having been passed or isovertaking for passing, quite frequently present such high intensitylight or glare reflected at the drivers eyes, that even his forwardvision is greatly interfered with, not to speak of the interference withvision when the driver is looking directly at the mirror to observe therearward field image therein.

The dangers arising from the described interferences with forward visionof the path over which the car is being driven or with vision of thefield to the rear are obvious both as immediate causative factors in thedevelopment of critical situations for drivers and as impairing to somedegree ability to handle a critical situation otherwise initiated.

Further a continuing reflection of headlights into a driver's eyes is atleast annoying, especially where the vehicles are maintaining a normallysafe spacing for some comparatively long period, and this of itself maybecome an unsafe driving situation either in contributing to the overalldifficulties of night driving by driver fatigue, or indirectly to theextent that, to eliminate the immediate glare problem the driver mayeither turn the mirror out of its normal position thus to a degreerendering the mirror non-functional or, alternatively, he may be duckinghis head sideways or grossly shifting his body from normal either to aposition or posture which is more tiring or which renders him less ableto respond quickly and well in his movements for vehicle operation, orto a position or posture where his eyes are out of a position allowingready use of either the glarereflecting mirror, or even of both mirrorswhere an inside and an outside or so-called "side-view mirror arepresent on the vehicle as is now standard for new passenger vehicles inthe United States.

Concern about the above stated problems is evident even in the patentedprior art proposals of various rearview mirrors intended to minimizefollowing headlight glare; such, for example as the use of a reflectingsilver layer applied to a somewhat finely roughened surface, expected todiffuse to some degree the glaring incident light; or use of anotherwise conventional reflecting silver surface in which many likerelatively narrow parallel unsilvered areas or stripes of uniform widthextend over the full horizontal length of the mirror, dividing themirror surface into silvered stripes of uniform larger width, with theunsilvered stripes having a width say one-third of the reflectivestripes so that one-fourth the total mirror area is unsilvered therebyto reduce the overall reflectivity of the mirror, but not reducing theintensity of the light actually reflected from the numerous andrelatively closely spaced silvered areas.

Further there has been proposed the use of materials in or as coatingsor screens, such as variable density filters, over a mirror surfacewhich by molecular or other sub-microscopic rearrangements change theirlight transmission characteristics, and hence the net mirror unitapparent reflective characteristics, in response to the intensity ofincident light.

There have been other quite different approaches to the problem,represented, for example, by proposals for a mirror unit, usuallyprismatic, mechanically tilted to displace a full-silvered surface usedas a daytime mirror, and bring into position as a night mirror anunsilvered surface having the reflectivity of a plain glass surfacegenerally approximately a 4 percent reflectivity; or for mechanicalintroduction of a light filtering screen either in the path of theincident or reflected light, either automatically under control ofphotocell devices sensing light intensity or in response to a specificdriver actuated control.

Such prior art approaches to the problem have had certain deflciences,such as lack of clarity or definition of the image of the rearwardfleld; or in the fact that, despite a reduction in overall reflectivityof the mirror, nonetheless the glare problem as a practical matter wasnot abated; or in diminishing the effectiveness of the mirror fordaytime or even nighttime driving use at times when following headlightswere not present or so located or used that glare would not be present.in devices where an entire mirror area for night driving has a verymarked reduction in reflectivity, either in the surface itself or byvirtue of interposed means attentuating incident or reflected light, orboth, a particular disadvantage is a diminution of depth perception forthe driver. In other prior proposals complexity of structure of use andmaintenance, or cost of production represent decided disadvantages.

By the present invention, even in an otherwise conventional mirror thereis provided, in the preferred fonn on a front silvered mirror, a singlecentral band extending transversally across the mirror as it is in use;which band has a reduced reflectivity as compared with adjacent saynormally reflecting areas, and of which the width, that is, verticaldimension, constitutes a sizable fraction of the total imaging mirrorarea such that by slight head tilting without gross bodily movements,the driver easily may as it were capture" and maintain followingheadlights in such band. With the headlights imaged in the area ofreduced reflectivity the glare problem is thereby abated, while yetproviding useful reflectivity in the band as well as normally reflectiveareas structure for a change of the net reflecting properties for theimaged field, either by mechanical tilting, screening or by varying thereflectivity of the actual imaging surface or transmissibility invariable density filters through light intensity responsive propertiesof components in the mirror structure or system.

Though description of a particular embodiment and general discussion ofthe invention may be in terms of a simple planar mirror or of an insidemirror, it is to be understood that the invention has application toinside and outside mirrors, also to curved mirrors and to mirrors in aperiscopic system, for providing day and night rearview vision,especially to the driver in an automotive vehicle.

It is then the general object of the present invention to provide asimple and improved safety type day-night rearview mirror for automotivevehicles.

Another object of the present invention is to provide a safety rearviewmirror for automotive vehicles affording in use means for eliminating orreducing the rearview vision interference and annoyance to the driverusually arising from the reflection of following vehicle headlights inconventional mirrors.

It is another object of the present invention to provide a safetyrearview mirror for automotive vehicles which provides, across therearward field-imaging area, a band of reduced reflectivity into whichimaged headlights of a following vehicle may be brought easily merely byslight head tilting motion of the driver, in the normal vehicleenvironment with conventional mirror mounting.

Another object is the provision of an improved motor vehicle rearviewmirrorof relatively low cost.

Other objects and advantages of the present invention will appear fromthe following description and drawings wherein:

FIG. I is an elevational view of one form of rearview mirror embodyingthe present invention with certain schematic designations appearingthereon;

FIG. 2 is a somewhat enlarged sectional view, taken as indicated by theline 2-2 in FIG. I; but with exaggeration of thickness of certainlayered structures;

FIG. 3 is a view similar to FIG. 2 representing modification of thepreferred form of the invention;

FIG. 4 is a view again similar to FIG. 2 showing a further embodiment ofthe invention;

FIG. 5 is a diagram, presented neither as optically geometrically nordimensionally accurate but merely indicating the mode of use of theimproved mirror in a passenger motor vehicle environment.

A preferred embodiment of the invention is represented by FIGS. 1 and 2of the drawings. In FIG. 1, the rearview mirror, as a whole designatedM, is shown as having a conventional horizontally elongated rectangularshape quite generally used in automotive vehicle inside rearviewmirrors, but with symbolic or schematic representation used for certainfeatures not otherwise readily represented.

Mounting means allowing tilting and horizontal pivoting of the mirror toan adjusted position in the vehicle convenient to the driver, for whichconventional structures are known, are not shown in FIG. 1, where themirror is simply shown disposed as in normal use with its lengthextending more or less horizontally or generally transverse of thevehicle.

In the somewhat enlarged sectional view of FIG. 2, thicknesses both ofthe substrate as well as of front or back surface coatings or layerstructure are greatly exaggerated for clarity of representation.

Thus though the mirror shown in FIG. 1 might have a width, i.e., height,say of 2% inches, and a length or horizontal dimension say of 12 inches,with a thickness perhaps on the order of one-eighth to one-fourth of aninch, reflective absorption or filtering layers or protective coatingswould have thicknesses on the order of perhaps no greater than a fewthousands of an inch with considerable differences even as between thethinner layers, so that, in the drawing, sections such as that of FIG. 2are in no respect proportional in dimensions of components appearingwithin the section, much less relative to FIG. I. It is likewise herenoted that in FIG. 5, hereinafter discussed, in no sense is there anyscaled or properly proportional representation of elements thereappearing nor geometrical correctness of light paths, sizes of angles ofincidence and reflection and the like, the figure being intended merelyto aid description of a mode of use and operation.

For its gross general shape the mirror M may have a plane form as morecommon for inside and outside rearview mirrors, or for mirrors inperiscopes; or it may be convex, either having curvature onlyhorizontally, as a portion of a cylindrical curface whether circularlycylindrical or otherwise, or having bi-directional curvature, verticallyand horizontally, as for example a portion of a spherical surface.

Whether the form be planar or convex, in the preferred form of theinvention, the mirror M comprises a substrate or support body 1 l whichis front silvered at layer 12; that is, the incident light does not passthrough the support to reach the reflective surface providing therearview field imaging area, though it is to be understood that acoating for protective or other purposes might be applied, even over theeffectively reflective front silvered layer, which coating obviouslywould be actually first encountered and traversed by incident light.

Moreover, the expression front silvered, unless context demandsotherwise, is to be understood as a designation of position or structurerather than composition, hence as comprising as well as silver otherreflective coatings which may be applied to the front" of the structure.

The substrate 11 has in addition to the front silvered surface 12, sodesignated as a whole, also a light absorptive back coating 13, such asblack paint, where the substrate is glass, as here represented and ascommonly used, or other transparent material.

Across the central region of the front surface 12 which defines theimaging area afforded to the driver by the mirror, in the particularform here shown, there is a strip-like zone or band 12b of an evenwidth, as hereinafter described, running the entire horizontal extent orlength of the mirror as a region of reduced reflectivity as comparedwith the normal reflectivity of the rest of the reflective surface 12represented by the upper and lower bands 12a and 12c.

The reduced reflectivity may be provided, for example, by producing 12bas a semi-silvered coating as contrasted with a full silvered coating in12a and 12c. Here semi-silvered is to be understood as meaning in thefirst instance merely a coating of diminished thickness or densityallowing a notable portion of the incident light to pass therethroughrather than being thereby immediately reflected.

The back coating 13 is used to render the back surface substantiallylight absorptive and thereby at the back surface of 11 to diminishreflection of the light passing through the semi-silvered band 12b.However, if the substrate itself provides sufficient light absorption ora substantially diminished reflectivity at the interface between theback of 12b and the front of the substrate 11, the coating 13 isunneeded.

Further by a preferred aspect of the invention, as symbolized in FIG. 1,by the horizontal parallel series of short oblique lines 12d-l2d, thelongitudinal margins of the band 12b merge into the adjacentlongitudinal normal reflective areas 12a, 120; that is, each boundaryrather than being'a sharp discontinuity is actually diffused by virtueof a gradually increasing heaviness or density of the reflectivematerial. This structural feature is an advantageous point ofpsychological design relative to eye response to the image fieldespecially since there is no sharp line evident to attract the eyes toor initially rivet vision on the boundary region.

With the middle band 12b of reduced reflectivity running straight overthe length of the mirror, thus to be horizontal in the normal useadjustment of the mirror in the vehicle, the middle band thus will behorizontally parallel to a road surface as viewed in the mirror; whichis also the criterion applicable for incorporation of the invention inconvex mirrors, leading there to a shape of the band drooping downwardto each side from the longitudinal center of he convex mirrors.

in the modification shown in FIG. 3, on the front of the substrate 21,an image area defining coating, as a whole designated 22, comprises anormally" reflective uniformly front silvered surface 22: over theentire area; and a band corresponding to 12b of FIGS. 1 and 2 isprovided here by a further light absorptive layer 22b applied on thecentral region of 22!, thereby to provide for a decreased reflectivityor attenuation of light such as that produced by the incandescent lampsof headlights. The layer 22b comprises a colored transparent substanceand may comprise a tape appropriately dyed to provide for lightabsorption to the required degree. Or the band 22b may, for example, bea coating sprayed by appropriate methods known to the such arts, inwhich case further the margins thereof may be thinned out orfeather-edged" to provide the same effect as in the diffuse margins 12ddescribed relative to FIG. 2.

The substrate 21 considered as a whole may itself be a light adsorptivematerial, substantially transparent, or again may be glass with a backcoating such as represented by 13 on 11 in FIG. 2.

in FIG. 4, the invention is shown embodied in a backsilvered mirror,wherein the substrate 31 is of course a transparent material, as glass,and the back silvered layer 32 has the structure of and may be formedafter the fashion as described for the front silvered layer 12 of FIG.2, to provide a horizontal cental band 32b, semi-silvered and thereforehaving reduced reflectivity, between the horizontally co-extensive upperand lower normally reflective bands 32a and 32c, with preferably againdiffused margins 32d or transition areas of changing reflectivitybetween 32b and the adjacent margins of 32a and 320. in this case aprotective and light absorptive coating 33 is applied at the back on theback silver layer 32.

In the reduced reflectivity band of the aforementioned mirror forms (theband 12b or analogous bands in other figures), the reflectivity is fromabout 4 percent to about 20 percent of the incident light, and in theareas 12a and 12c, here for convenience termed full silvered areas, thereflectivity is from about 40 percent to about percent of the incidentlight from sources as auto headlights.

For the average full size passenger vehicle, therefor for the driverhead heights and eye spacings from the mirror placements used thereinfor inside and outside mirrors, the margin bands l2dl2d have a minimumpractical width of one-eighth inch, about threesixteenths inchpreferred; and while for band 12b a minimum width of three-eighths inchmay for some situations have some utility, a 9/16 inch width ispreferred minimum for inside mirror use; and for outside mirror use, a5% inch to 34 inch minimum width; the bands 12d of 16 inch width beingpresent additionally to the band 12b in such cases. For mirrors mountedhigher above the road, therefore higher above usual headlightelevations, as outside mirrors on trucks, an increased mini mumnine-sixteenths of about nine-sixteenth inch is indicated. Ordinarily,increasing the width to greater than 1 inch is of little value, andneedlessly reduces the higher reflective areas. Thus on a slim insidemiror 2 inches wide, the zone 12b would occupy from about 20 to 40percent of the mirror width.

The mirror is disposed in the location usual for its mirror type in anautomotive vehicle with a conventional mounting sufficient. For example,as an inside mirror in a passenger vehicle the mirror is mounted forwardof, and at or slightly above eye level for, the normal or averagedriver. Usually then the designed mirror size and location are such thatwith the mirror set for the driver's normal posture in driving, themirror as a whole will image substantially the entire vertical andhorizontal extent of the vehicle rear window. The band 121; then will beimaging the central transverse portion of the rearward field defined bythe rear window; or as the driver views it, the band 12b appears to beimaged on or projected upon the middle of the rearward vision field orcentrally across the rear window; occupying a substantial fraction ofthe vertical extent of the field of view.

in the purely schematic and generalized FIG. 5, as in a vehicleenvironment of use, the left vertical line M represents the mirrorreflective surface; the vertical line W, the vertical extentorprojection of the vehicle rear window; and the subscripted symbol E,the driver's eye at slightly different vertical positions. With mirror Mset by vertical tilt adjustment for the drivers normal driving postureand head position as indicated by the central symbol Ex to have the band12b appear, as it were, projected across or imaged (as represented bythe x symbol at ix) in the central region of the rear window, (themirror of course also set in horizontal sense to span the windowtransversely), only a slight upward inclination of the driver's head,bringing the eyes to position Ey shifts the transverse image of the band12b to appear at the lower portion of the window as indicated by thestraight line at ly; while with similar slight shift downward to the eyeposition Ez, the band appears to be imaged at the upper portion of therear window as indicated the dashed straight line lz, also to the rightof line W. Also in night conditions, the driver can set his mirror tothe usual preferred disposition with the rearward horizon approximatelyon the center of the band 12b in the image display and this maintainsthe majority of encountered rearward headlights imaged in the reducedreflectivity band.

Considering the situation conversely in terms of incident light fromrearward headlights, obviously if the light is entering the window alonga path corresponding to the line of projection or imaging of the band12b for a given eye position, it will be reflected to the driver's eyefrom the mirror band 12b and hence will be attenuated or reduced inintensity to obviate the glare. If by changing vertical road levels orangles or by changing intervehicle spacing, the path of the incidentlight, (that is, its angle of incidence) changes, only a very slighttilting head shift is required to keep the following lights in the bandof reduced reflectivity from the drivers eye view point.

For an example of use by a driver in a typical environment, a flatmirror M (12 inches long and 2% inches wide with a band 12b of about 9/16 inch width, and additionally margin bands 1211-1211 eachthreesixteenths inch wide, and representing an embodiment as abovedescribed for FIGS. 1-2) was merely secured to the original equipmentmirror mounting in a four door sedan, where the distance from the mirrorM to the top edge of a sloping rear window was about 63 inches, withprojected vertical span of the windows as at W in FIG. about 11 inchesfor an actual slope dimension of inches. By rough measurements, with adriver in his normal posture and the mirror being slightly (about 1inch) above eye level, the mirror-toeye (mid-eyes to mid-mirror)distance was about 27 inches; a darkened stripe representing theprojection of the band 12b (Ix in FIG. 5) and some part of the marginsl2d-12d occupied roughly the middle third of the apparent rear windowimage; and could be shifted to a bottommost position as at ly by anupward head tilt represetting about 1% inch eye shift; and to a topmostposition as at lz by a downward tilt representing again about 1% incheye shift. In other words, shift from a bottom to a top position occuredby a total tilting excursion of the eye of only 2% inches, in asituation where the band 12d of 9/16 inch width at 27 inches subtendedvertically an eye angle of about 1.3". For a 20% inch spacing, a darkband occupying the middle half was shifted to top and bottom positionsby respective 94 inch head tilts or only 1% inch total excursion. Themeasurements having been rough, no attempt is made to reconcile theresults at the two spacings or the physical geometry.

It has been found by actual experience of average passenger vehicledrivers, with a mirror as described in that example installed at theplace of a conventional original equipment plane mirror, that after onlya fraction of an hour of night driving on thruways and the like, theslight head tilting under differing circumstances to capture troublesomeheadlights in the attenuating zone or band became practically automaticwithout thought, as a quickly acquired habit; the driver, whileattending to his forward driving vision, automatically and readilytilting his head slightly as needed to maintain the "capture" of thefollowing headlights in I the band 12b, even with changing vehiclespacing as in being overtaken by the following vehicle. The diffusedmargins l2dl2d, on the order of one-eighth inch wide, eliminated anyuntoward effects which would arise by sharp discontinuity between theattenuating zone and the fully silvered areas.

1t was further found by actual trial, with reduction of reflectivity tothe percentage above indicated in a front silvered mirror as describedfor FIGS. 1 and 2, that in the zone represented by band 12b sufficientvision was maintained of the following vehicle for safe observation,while yet the glare problem was obviated; while further above and belowthat the band or zone, e.g., where the same is at mid-height of theimaged field, clear vision and contrast was available. On the otherhand, for daytime driving again effective rear vision is afforded in thetotal mirror arrangement. For day and for night driving, depthperception was provided. Though an intermediate reflectivity can also beusedin the lower band at 12c in P10. 1, this has not been foundnecessary as a practical matter for a mirror of conventional size forpassenger vehicle use.

1 claim:

1. For an automotive vehicle, a safety day and night driving rearviewmirror providing as mounted functionally in a normal vehicleenvironment, a reflective imaging area for the driver and having ahorizontal extent and a vertical extent and comprising:

in said imaging area, a band over said horizontal extent havingreflectivity reduced to a degree that, from following vehicle headlightsimaged on the said band, glare is dimished to a level noninterferingwith safe night driving vision of a driver;

said band extending across the functional horizontal extent of saidimaging area above and adjacent a portion of said imaging area havingmarkedly higher reflectivity;

said band and portion merging into each other in a margin regiongradually increasing from the low reflectivity of said band to thehigher reflectivity of said portion;

said band having a vertical dimension sufficient to enable the drivereasily to maintain the image of following headlights within said band byslight tilting of the head, even with changing inter-vehicle spacing.

2. A safety rearview mirror as described in claim 1,

wherein:

said imaging area is horizontally elongated and planar and includesareas of higher reflectiyity both above and below and horizontallyco-extensive with said band.

3. A safety rearview mirror as described in claim 2,

wherein:

both the upper and lower margins of said band merge through regions ofincreasing reflectivity into said areas of higher reflectivity.

4. A safety rearview mirror as described in claim 1, wherein:

said reflective imaging area is provided as a front silvered surface ona substrate conventionally mountable in a vehicle environment.

5. A safety rearview mirror as described in claim 4,

wherein:

said band is provided as a semi-silvered portion of said front silveredsurface.

6. A safety rearview mirror as described in claim 1,

wherein:

a layer of light filtering or absorbant material is applied in a bandover an imaging area of uniform reflectivity to provide a said band ofreduced reflectivity whereby said glare is diminished to a levelnon-interfering with safe night driving vision of an average driver. 7.A safety rearview mirror as described in claim 1, wherein:

said reflective imaging area is provided as a front silvered surface ona glass substrate having on its back surface a light absorptive layer;

said band is provided as a semi-silvered portion of said front silveredsurface between upper and lower more fully silvered areas of highreflectivity; both horizontal margins of said band merge through regionsof increasing density and reflectivity into said areas of higherreflectivity. 8. A safety rearview mirror as described in claim 7,wherein:

said band of diminished reflectivity has a vertical dimension greaterthan about three-eighths inch. 9. A safety rearview mirror as describedin claim 1, wherein:

said imaging area includes areas of higher reflectivity above and belowand horizontally co-extensive with said band; and said band is shapedover its horizontal extent to appear horizontally parallel to a roadsurface as viewed by the driver in said mirror. 10. A safety rearviewmirror as described in claim 1, wherein:

in said vehicle at a distance from a vehicle designcontemplated averageposition of a drivers eyes,

the said band in vertical extent subtends an angle of about l.3 in avertical plane extending from said position to said mirror.

1]. For an automotive vehicle, a safety day and night driving rearviewmirror providing, as mounted functionally in a normal vehicleenvironment, a reflective imaging area for the driver and having ahorizontal extent and a vertical extent and comprising:

in said imaging area, a band running over said horizontal extent, havingreflectivity reduced to a degree that, from following vehicle headlightsimaged on the said band, glare is diminished to a level noninterferingwith safe night driving vision of a driver; said band extending acrossthe functional horizontal extent of said imaging area between upper andlower portions of said imaging area each having reflectivity markedlyhigher than said band;

said band and each said portion merging into each other through arespective margin region having reflectivity gradually increasing fromthe low reflectivity of said band to the higher reflectivity of therespective said portion;

said band having a vertical dimension sufficient to enable the drivereasily to maintain the image of following headlights within said band byslight tilting of the head, even with changing inter-vehicle spacing.

1. For an automotive vehicle, a safety day and night driving rearviewmirror providing as mounted functionally in a normal vehicleenvironment, a reflective imaging area for the driver and having ahorizontal extent and a vertical extent and comprising: in said imagingarea, a band over said horizontal extent having reflectivity reduced toa degree that, from following vehicle headlights imaged on the saidband, glare is dimished to a level non-interfering with safe nightdriving vision of a driver; said band extending across the functionalhorizontal extent of said imaging area above and adjacent a portion ofsaid imaging area having markedly higher refLectivity; said band andportion merging into each other in a margin region gradually increasingfrom the low reflectivity of said band to the higher reflectivity ofsaid portion; said band having a vertical dimension sufficient to enablethe driver easily to maintain the image of following headlights withinsaid band by slight tilting of the head, even with changinginter-vehicle spacing.
 2. A safety rearview mirror as described in claim1, wherein: said imaging area is horizontally elongated and planar andincludes areas of higher reflectivity both above and below andhorizontally co-extensive with said band.
 3. A safety rearview mirror asdescribed in claim 2, wherein: both the upper and lower margins of saidband merge through regions of increasing reflectivity into said areas ofhigher reflectivity.
 4. A safety rearview mirror as described in claim1, wherein: said reflective imaging area is provided as a front silveredsurface on a substrate conventionally mountable in a vehicleenvironment.
 5. A safety rearview mirror as described in claim 4,wherein: said band is provided as a semi-silvered portion of said frontsilvered surface.
 6. A safety rearview mirror as described in claim 1,wherein: a layer of light filtering or absorbant material is applied ina band over an imaging area of uniform reflectivity to provide a saidband of reduced reflectivity whereby said glare is diminished to a levelnon-interfering with safe night driving vision of an average driver. 7.A safety rearview mirror as described in claim 1, wherein: saidreflective imaging area is provided as a front silvered surface on aglass substrate having on its back surface a light absorptive layer;said band is provided as a semi-silvered portion of said front silveredsurface between upper and lower more fully silvered areas of highreflectivity; both horizontal margins of said band merge through regionsof increasing density and reflectivity into said areas of higherreflectivity.
 8. A safety rearview mirror as described in claim 7,wherein: said band of diminished reflectivity has a vertical dimensiongreater than about three-eighths inch.
 9. A safety rearview mirror asdescribed in claim 1, wherein: said imaging area includes areas ofhigher reflectivity above and below and horizontally co-extensive withsaid band; and said band is shaped over its horizontal extent to appearhorizontally parallel to a road surface as viewed by the driver in saidmirror.
 10. A safety rearview mirror as described in claim 1, wherein:in said vehicle at a distance from a vehicle design-contemplated averageposition of a driver''s eyes, the said band in vertical extent subtendsan angle of about 1.3* in a vertical plane extending from said positionto said mirror.
 11. For an automotive vehicle, a safety day and nightdriving rearview mirror providing, as mounted functionally in a normalvehicle environment, a reflective imaging area for the driver and havinga horizontal extent and a vertical extent and comprising: in saidimaging area, a band running over said horizontal extent, havingreflectivity reduced to a degree that, from following vehicle headlightsimaged on the said band, glare is diminished to a level non-interferingwith safe night driving vision of a driver; said band extending acrossthe functional horizontal extent of said imaging area between upper andlower portions of said imaging area each having reflectivity markedlyhigher than said band; said band and each said portion merging into eachother through a respective margin region having reflectivity graduallyincreasing from the low reflectivity of said band to the higherreflectivity of the respective said portion; said band having a verticaldimension sufficient to enable the driver easily to maintain the imageof following headlights within said band by slight tilting of the head,even with changing inter-vehicle spaciNg.